To determine whether the initial use of two NRTIs + NFV followed by two different NRTIs + EFV is superior to the intial use of two NRTIs + EFV followed by two different NRTIs + NFV. To determine whether initial use of two NRTIs + NFV + EFV is superior to either of the two consecutive 3-drug regimens listed above. To determine whether 3TC/ZDV followed by ddI+d4T is superior to ddI+d4T followed by 3TC/ZDV when these two NRTI combinations are taken with NFV or EFV.